Ian Desmond went 4 for 4, Michael Morse had four hits and Tyler Moore also connected for the Nationals, who had a season-high 21 hits, which tied the club mark since the team moved to Washington in 2005.

They had 11 extra-base hits, the most since becoming the Nationals.

Dexter Fowler and Jonathan Herrera homered and Jordan Pacheco had three hits for the Rockies, who have dropped 15 of 19.

Gio Gonzalez (10-3) picked up the win despite allowing five runs, four earned, on eight hits in six innings. He struck out seven.

Zimmerman entered the game with 998 career hits and reached the 1,000 mark in his third at-bat, a single to right in the fifth inning. He added his fourth home run of the season in the sixth to finish with three hits.

The game was close when the Nationals broke it open in the fifth against reliever Guillermo Moscoso. Desmond had a two-run double and Moore a three-run homer in a five-run outburst that made it 9-3. Zimmerman hit a solo homer and LaRoche hit his second of the game, a two-run shot, in the sixth to make it 12-4.

Moscoso gave up eight earned runs in just 1 2-3 innings.

Working within the 75-pitch limit set by the Rockies, starter Christian Friedrich (4-5) left after retiring Bryce Harper on his 70th pitch to lead off the fifth. He allowed four runs on nine hits and struck out three in 4 1-3 innings.

LaRoche put Washington up 1-0 in the second with his 14th home run of the season. Morse's two-run double in the third made it 3-0.

Colorado tied it in its half of the inning on Carlos Gonzalez's RBI double and run-scoring singles from Michael Cuddyer and Todd Helton. Cuddyer scored on Harper's throwing error to make it 3-3.

Gio Gonzalez made it 4-3 with a two-out RBI single in the fourth.

NOTES: Before the game, Rockies pitching coach Bob Apodaca asked to be reassigned and he was made a special assistant to GM Dan O'Dowd. Bullpen coach Jim Wright and Triple-A pitching coach Bo McLaughlin will serve as co-pitching coaches for the remainder of the season. ... LaRoche now has 17 career multihomer games. ... The Nationals will send RHP Jordan Zimmermann (3-6) to the mound Wednesday. The Rockies are expected to call up LHP Edwar Cabrera from Double-A to start for Colorado.

Paul DeJong handed the Nationals their second straight walk-off loss, capping a back-and-forth finish with a game-ending solo homer in the ninth inning of the St. Cardinals' 7-6 victory Monday night.

DeJong took Koda Glover (0-1) deep leading off the ninth on a 3-1 pitch. A night earlier, Ryan Madson allowed a game-ending ninth-inning grand slam to the Chicago Cubs' David Bote in a 4-3 defeat.

"I don't sleep most nights, I like to watch replays of the game," Martinez said. "And last night was no different."

Washington's bullpen has blown saves in three of its past four games. All-Star closer Sean Doolittle has been on the disabled list since early July, and top setup man Kelvin Herrera went to the DL with right rotator cuff impingement last week.

"I don't know what else to do," Martinez said of the bullpen.

The usually stoic DeJong wasn't quite sure how to celebrate his first career walk-off homer. He started calm, keeping his head down as he rounded the bases. After coming around third, though, he whipped his helmet into the grass, threw his arms down and bellowed out a roar.

"My first walkoff, it felt so good I had to do something a little different," DeJong said.

The Cardinals recorded their 10th walkoff of the season and DeJong became the sixth different player to end a game in grand fashion.

"They're all special, all emotional," St. Louis interim manager Mike Shildt said. "These guys have the mentality, `Do your job, keep the line moving.' They have a lot of trust with each other."

The Cardinals have won six in a row and moved to nine games over .500 for the first time this season.

DeJong's 380-foot drive ended a wild final two innings.

Matt Carpenter and Jedd Gyorko homered in the eighth inning to put St. Louis up 6-4. Gyorko started the rally with a leadoff drive, and Carpenter followed with a three-run homer off Sammy Solis.

The Nationals tied it at 6 in the top of the ninth on RBI singles by Daniel Murphy and Matt Wieters off closer Bud Norris. Dakota Hudson (3-0) relieved Norris and stranded two baserunners by retiring Wilmer Difo and Adam Eaton.

Juan Soto and Bryce Harper homered for the Nationals, who have lost five of seven.

Gyorko sparked St. Louis' big eighth inning with his homer off Justin Miller. Kolten Wong and Patrick Wisdom then singled to set up Carpenter's 33rd homer. Carpenter has homered in seven of his past 10 games. He extended his major-league leading on-base streak to 31 games with a first-inning bunt single. He has 17 homers during that string.

Harper won a 10-pitch battle with starter Miles Mikolas by drilling his 29th homer leading off the fourth to lead 2-1.

Ryan Zimmerman added a run-scoring double in the second for the Nationals.

Jose Martinez had four hits for the Cardinals.

Mikolas gave up four runs on four hits over seven innings. He struck out four and walked one.

Tommy Milone started for Washington and gave up two runs on 10 hits over 4 1/3 innings.

Ryan Zimmerman is on a hot streak for the Washington Nationals, and he was named NL Player of the Week, the league announced Monday.

Quite frankly, this isn't exactly a surprise.

The Nats' 33-year-old slugger completed a wild week going 10-for-21, finishing with a .476 batting average along with a .538 on-base percentage and slugging at 1.048.

He particularly stunned in Washington's 9-4 victory over the Chicago Cubs on Saturday, blasting two homers and driving in six runs. The first baseman finished the week with 12 RBI in seven games, along with three total dingers and three doubles.

Zimmerman returned to the Nats' lineup on July 20 off the 60-day disabled list after being out since the beginning of May with an oblique injury. Since his return, in 15 games, he's batted .354 with four home runs and 18 RBI after going onto the list hitting just .217.

Other Nats who have previously won the NL Player of the Week Award this season are Max Scherzer, Mark Reynolds and Adam Eaton.